All small-arms ammunition made today is composed of propellant, metal case, bullet and primer. The latter initiates ignition after a sharp blow from the firearm’s hammer or striker, and its location determines whether the cartridge is a member of the centerfire or rimfire family.
Experienced gun owners can tell the difference fast, but it’s critical that every enthusiast gets intimately familiar with identification. The styles are not interchangeable, even when bullet diameters are identical. In fact, they won’t operate in a gun made for the other design. Inadvertently mixing or trying to force them to work is dangerous.
Thankfully, gun and ammunition companies adhere to guidelines from the Sporting Arms and Ammunition Manufacturer’s Institute (SAAMI), which make it nearly impossible to chamber and touch of an incorrect combination. Regardless of that safety record, though, the first line of defense is the individual shooter.
It’s easy to determine whether ammunition is centerfire or rimfire. Simply inspect the end of a cartridge opposite the bullet (the head/base). If there’s a component in the center of that flat surface it’s a centerfire. If nothing is inserted or sealed there, the primer is internal and applied around the entire circumference of the case rim. That makes it a rimfire.
Both styles of cartridge operate by a simple principle. The primer, struck by sufficient force, sends spark and flame into propellant (powder) in the cartridge case. It, in turn, burns and generates gas. Pressure builds during that process and once high enough it forces the bullet down and out of the barrel.
Either cartridge design can ring steel, stop criminal attacks and take game, but what they do best is far from identical. Centerfires, on average, provide improved downrange and terminal performance, making them the top choice for big-game hunting, self-defense and long-distance shooting. Rimfires, on the other hand, produce less recoil, are budget-friendly—assuming no shortages like 2020 and 2021—save storage space and shave weight. They are adept at harvesting small game, but illegal for the take of larger animals in most regions.
Frenchman Louis-Nicolas Flobert invented the first rimfire metallic cartridge in 1845, but his goal wasn’t improved hunting. His .22-caliber loads consisted only of a primer, case and bullet. There was no powder, so muzzle velocity came in at roughly 700 fps, ideal for his other introduction that year—parlor guns. Shooting in the house became somewhat fashionable among societies elite, although the pastime likely gained more traction at outdoor gatherings.
Similarly low-velocity loads, ideal for dispatching pests with minimal risk of bullet escape, are still available. Today’s .22 CB ammunition is a favorite among farmers and ranchers who routinely deal with animal damage or the occasional need to haze off wildlife.
The .22 Short rimfire was introduced in 1857, along with a gun to run it—the first revolver to come out of the Smith & Wesson factory. The .22 Long followed in 1871 then the .22 Long Rifle arrived in 1887.
Bigger-bore rimfires also appeared, with the most notable examples being the .44 Henry and .56-56 Spencer. Both saw use during the Civil War.
Centerfire was First
It was early in the 1800s when Jean Samuel Pauly introduced the first centerfire cartridge. The Swiss invention was upstaged later when a different version appeared in 1829, although improvements on it continued until 1855. Throughout the years some of the biggest names in gun making and early ballistics polished the approach, making it the performer it is today.
Despite being the eldest of the metallic-cartridge designs, it wasn’t until the appearance of the .44-40 WCF (Winchester Centerfire) and lever-action rifle to chamber it—the famed Winchester Model 1873—that it went mainstream. The year was 1873 and it wasn’t long until militaries across the globe recognized the additional downrange performance and flatter trajectory.
Rimfire manufacturers face a tough challenge, though. To start, the application of primer compound must be even across the entire circumference of the rim, internally, with minimal—preferable no—center spillover. Modern machinery is adept at getting the job done in those ever-reliable and popular 500-round bricks of .22 Long Rifle ammo, but the approach isn’t consistent enough to witness the full accuracy potential. Identical application of that primer ensures consistent ignition speed and spread, shot-to-shot.
It’s .22 rimfires that claim Olympic Gold, after all. Not long ago—and likely still—only the most experienced workers at each factory oversaw the process. Those watchful eyes babysit the match-grade ammo that wins on 10-, 25- and 50-meter firing lines every four years at the Summer Olympics and on most weekends across the nation.
The primer isn’t the only component under tight control, though. To ensure bullet speed is as close to identical as possible with each shot, the propellant is measured meticulously. And, the best loads usually launch the bullet at a reduced velocity. There’s more involved in creating match-grade rimfire ammo, which explains why it’s always slightly more expensive. If you want to shrink groups with minimal recoil, though, there’s no denying it is the way to go.
Centerfires, on the other hand, have their primer mechanically seated in a hole the cartridge’s case. With the depression and flash hole in front created during the case’s construction, machinery performs the task with enviable precision. Regardless, that powder will ignite from the middle instead of around its entire circumference at the base.
Those tight tolerances make cartridges on the market exceptionally accurate. It’s still not good enough for some enthusiasts, who dial things in further downrange by reloading centerfire cases. They take tedious notes, fine-tune loads and win competitions with home brews regularly. Others do so to save money. It’s a great hobby, but it is not one possible with rimfires, at least economically.
Centerfire or Rimfire
Militaries worldwide and big-game hunters universally acknowledge centerfire cartridges offer the best performance for their needs. The cartridges are unfailing in reliability and hit with authority at distance. Add modern bullet design’s breeze-bucking profiles and long-range trajectory is more predictable, repeatable and precise than ever before.
They are, however, more expensive than rimfires. Recoil is stouter and when ammunition shortages hit unexpectedly it’s hard to find the right cartridges on the shelf.
Rimfires are less expensive, but the requirement that the case’s rim bend enough to set off the primer sets an unavoidable upper pressure limit. Bullet weight is another factor, reducing the amount of energy it delivers downrange. That fact also makes them more susceptible to wind drift.
The gap in performance, however, continues to shrink. The .22 WMR (Winchester Magnum Rimfire) already had a sterling reputation, but the introduction of hotter loads like the .17 HMR (Hornady Magnum Rimfire) and others rimfires are steadily gaining ground.
Modern Sporting Rifle Use
There’s no shortage of AR-15s on the market today chambering a variety of centerfires, and whether they use direct gas impingement or a piston-driven system, they run relatively clean. Carbon buildup and fouling are unavoidable on any gun, and the amount of maintenance required depends on it and the ammunition. They aren’t the dirtiest running designs ever made, though.
Most, if not all, rimfire versions of AR-15 uppers run on a blowback design. Conversely, it’s not the cleanest system around. That’s not to say it’s unreliable, but if you don’t look forward to scrubbing after every range session, it’s another consideration.
Which Is Best?
There’s no denying the downrange performance of centerfire cartridges is superior to rimfires, which makes them the ideal choice for big-game hunters, long-distance shooters, and the military. The best cartridges are significantly more expensive, but bulk packs of FMJ 5.56 NATO and a few others go on sale with regularity. When they do, it allows high-volume shooting without crippling a budget.
The overwhelming majority of experts point to centerfire’s superior ability to stop a criminal as the reason it’s the top self-defense choice. The discussion is, however, blurred by the fact that nearly all life-threatening encounters take place up close and personal. The judicial system takes a dim view of shooting a criminal at distances beyond 10 yards (most cite 7 yards), well within a rimfire’s range. The tiny entry wound is a big drawback, but that reduced recoil speeds follow-up shots, if necessary, and is confidence-building for many shooters. As a result, the popularity of carry handguns chambered in .22 Winchester Magnum Rimfire or even .22 LR continues to grow.
The biggest advantage to rimfire, though, is the modest cost. If hours of firing line time and plinking fun is the goal, find at least one .22 LR-chambered gun and you’re all set to go. Get one set up just like your AR, and you’re also committing muscle memory to those fire controls and building an intimate knowledge of operation.
Most enthusiasts own a mix of centerfires and rimfires. Some firearms are there for opening day of big-game season and if the unthinkable happens. The others are better suited for small game and fun-filled hours of practice. And both complete their missions with undeniable reliability.